Starlight Glimmer abandoned her plan to travel back in time when Prince Dusk Shine showed her that Equestria would be destroyed if she continued to alter the past, so she pretended to reform, although her new friends do not really trust her.
However, Starlight is secretly planning revenge without destroying Equestria in the process, this time without friendship and without the Mane 6 standing in her way, or so she wants to believe, as she has begun to feel more than just sympathy towards the prince of friendship, which will make his new revenge plans difficult.